Pointer to incomplete class type is not allowed

Solution 1:

An "incomplete class" is one declared but not defined. E.g.

class Wielrenner;

as opposed to

class Wielrenner
{
    /* class members */
};

You need to #include "wielrenner.h" in dokter.ccp

Solution 2:

One thing to check for...

If your class is defined as a typedef:

typedef struct myclass { };

Then you try to refer to it as struct myclass anywhere else, you'll get Incomplete Type errors left and right. It's sometimes a mistake to forget the class/struct was typedef'ed. If that's the case, remove "struct" from:

typedef struct mystruct {}...

struct mystruct *myvar = value;

Instead use...

mystruct *myvar = value;

Common mistake.

Solution 3:

You get this error when declaring a forward reference inside the wrong namespace thus declaring a new type without defining it. For example:

namespace X
{
  namespace Y
  {
    class A;

    void func(A* a) { ... } // incomplete type here!
  }
}

...but, in class A was defined like this:

namespace X
{
  class A { ... };
}

Thus, A was defined as X::A, but I was using it as X::Y::A.

The fix obviously is to move the forward reference to its proper place like so:

namespace X
{
  class A;
  namespace Y
  {
    void func(X::A* a) { ... } // Now accurately referencing the class`enter code here`
  }
}

Solution 4:

I came accross the same problem and solved it by checking my #includes. If you use QKeyEvent you have to make sure that you also include it.

I had a class like this and my error appeared when working with "event"in the .cpp file.

myfile.h

    #include <QKeyEvent> // adding this import solved the problem.

    class MyClass : public QWidget
    {
      Q_OBJECT

    public:
      MyClass(QWidget* parent = 0);
      virtual ~QmitkHelpOverlay();
    protected:
        virtual void  keyPressEvent(QKeyEvent* event);
    };